This invention relates to the field of display systems, more particularly to lamp timers used by projection display system.
Display system manufacturers are under increasing competitive pressure to improve the brightness of their displays. Bright displays are much more appealing to consumers. Brighter projectors can project larger images, a very desirable feature in the consumer projection display market. Bright projected images are easier to see, especially in venues that suffer from a high ambient light level.
High pressure arc lamps provide a very bright light source and enable projection display systems to produce high quality bright images. Unfortunately, high pressure arc lamps degrade with usage and have a finite rated lamp life. By the end of the rated lamp life, the high pressure lamp is typically only half as bright as it was at the beginning of its life. Thus, the image quality of a display using a typical high pressure lamp degrades over time. While many consumers will replace the lamp, many will continue to use the lamp and accept the degraded image.
High pressure lamps are an explosion hazard. The risk of explosion increases as the lamp is used, and most likely for lamps that are used past their rated lifetime. A lamp explosion easily can damage the projector, and explosion of some high pressure lamps, for example Xenon lamps, can send shrapnel through the projector housing and injure anyone in the vicinity of the projector.
Thus, the use of high pressure lamps poses a safety risk to the consumer. Safety is a primary concern when designing and manufacturing consumer electronics. Not only must the products be safe as designed and manufactured, but every effort is made to ensure the article remains safe even if it suffers a reasonable level of abuse or misuse at the hands of the consumer.
In many applications that use arc lamps, timers track the time the arc lamp is on and warn the operator to replace the bulb at the end of the lamp lifexe2x80x94before risking an explosion. The timer resets each time the lamp is replaced, and warns the operator when to order a replacement lamp and when to install the replacement lamp. A simple timer is often sufficient in industrial applications where the operator has been trained to replace the lamp, knows to have replacement lamps on hand, and is generally concerned with keeping the equipment in peak operating condition.
Average consumers cannot be relied on to replace the lamps in home-use equipment. The consumer may not feel competent replacing the lamp, or may simply want to put off replacing the lamp until a more convenient time. This delay can easily lead to an eventual explosion of the lamp, harming the consumer and damaging the projector. To avoid this risk, displays using high pressure lamps may be designed to automatically shut down once the lamp timer reaches a predetermined value. The timers described above, however, are easily defeated merely by removing and replacing the lamp.
Another problem with a simple automatic timer involves determining the rated life time of a new lamp. Unless the display device can rely on assistance from the consumer, the display system must be preset with the rated lifetime of the lamp. If a display system is designed to accept more than one lamp model, the preset value must be the shortest life of any of the interchangeable lamps. This results in premature replacement of longer-life lamps. Furthermore, manufacturers often improve the design of a lamp over the course of production. While these design improvements can increase the rated lifetime of the lamp, if the expected lifetime of the lamp is hard wired in the projector, the benefits of the lamp improvements will not be realized.
More sophisticated timers could prevent the consumer from simply reinstalling the same bulb. These more sophisticated timers, however, must be able to operate in a very harsh environment. Not only does the lamp put off a large amount of heat, igniting the lamp arc creates huge electromagnetic impulses that can easily reset electrical circuits and overwrite ordinary electrical memory devices. What is needed is a reliable timer that is difficult to defeat or reset.
Objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention that provides a method and system for a reliable lamp life timer and method. One embodiment of the claimed invention provides a method of tracking the elapsed operating time of a light source. The method comprises the steps of: associating a memory device with a lamp, igniting the lamp, updating an elapsed lamp on time value stored in the memory, comparing the elapsed lamp on time to the rated lamp life value, repeating the updating and comparing steps until the elapsed lamp on time exceeds the rated safe life value, and disabling the lamp when the elapsed lamp on time exceeds the rated safe life value. Alternate embodiments store the values stored in multiple locations of the memory device, comparing the values read from the multiple locations, and rewrite inaccurate locations.
A display system comprising: a lamp, a memory device, a timer controller circuit, a spatial light modulator, and projection optics. The lamp for generating a beam of light along a light path. The memory device associated with the lamp and storing the rated safe life value. The timer controller circuit capable of reading the rated safe life value from the memory and storing an elapsed lamp on time value in the memory. The timer controller circuit disabling the lamp when the elapsed lamp on time value exceeds the rated safe life value. The timer controller circuit also disabling the lamp when either the elapsed lamp on time value or the rated safe life value become irretrievably corrupted. The spatial light modulator modulating the beam of light to produce a modulated beam of light that is focused on an image plane by the projection optics.